Chronicle file A Muskegon County Road Commission truck plows snow after a winter storm in 2008.

WEST MICHIGAN — Michigan's snowplow trucks operating on icy routes in the state's southwest region will be slowing down to conserve salt this winter.

In Muskegon and Ottawa counties, the slower speed is already being used by the road commissions.

Michigan Department of Transportation officials announced this week that their trucks will be traveling only 25 mph while spreading salt on the state routes in a nine-county region from Allegan County south to the border. They said they expect the slower speed — a reduction from the previous speeds between 35 and 45 mph — to improve effectiveness and save money.

The Muskegon County Road Commission already follows a similar standard for its snowplow trucks. The local road agency's maintenance superintendent, Laurie Peterson, said the speed range is 25-30 mph for Muskegon County's trucks.

The trucks travel at those speeds when laying down salt “because we want it to penetrate and not bounce off,” Peterson said. The 25-30 mph range also is recommended for plowing snow to limit the snow flying off the blade and potentially causing injuries or property damage, she said.

Brett Laughlin, the Ottawa County Road Commission’s managing director, said his drivers generally go about 25 mph if they are spreading salt. If just plowing, they go 35 mph.

“If you go over 25 mph with salt, you’re not keeping it on the road like you should,” he said.

The slower speed reduces the bounce and scatter of salt off the roadway.

In addition to county roads, the Muskegon County Road Commission and Ottawa County Road Commission plow all the state highways in their respective counties through contracts with the state.

That is not the case in the southwest region, home to the pilot program this year. Counties in that region are Allegan, Barry, Berrien, Branch, Calhoun, Cass, Kalamazoo, St. Joseph and Van Buren.

Nick Schirripa, MDOT spokesman for the southwest Michigan region, said the state trucks directly handle the M-routes, US-routes and interstates in most of those nine counties rather than contracting with the local road commissions.

By reducing the speed of its trucks, MDOT expects to use 30-40 percent less salt this season in the region and save more than $100,000 in annual costs.

“If this ends up costing the taxpayers less money in salt every year, I would say it's a success,” Schirripa said.

MDOT officials caution motorists in the pilot-program region to be aware of the slower trucks.

“This change in our salting practices is designed to reduce costs and increase our effectiveness and efficiency,” said MDOT Southwest Region Maintenance Superintendent Rich Hassenzahl. “But safety is always the top goal. While the roads will be salted better this way, motorists still need to be aware of our plow trucks moving at a slower speed, especially on our freeways.”